The human immunodeficiency virus (or HIV) is a retrovirus of the genus Lentivirus, i.e. a virus with a long period of incubation, which implies slow development of the disease.
Like all viruses, HIV is incapable of multiplying on its own. It must first invade a cell and take control of it. The target cells of HIV are those presenting CD4 receptors on their surface. Thus, CD4+ T lymphocytes, macrophages, dendritic cells and cerebral microglial cells can be infected with HIV.
When HIV infects a target cell, it takes control of it. Then the virus begins to make new copies of itself: this is the reproduction or replication phase. The virions thus produced infect other cells. In the absence of treatment, experts estimate that HIV can make up to 10 billion viral copies per day.
Two serotypes of HIV have been identified to date: HIV-1, which is present in most countries in the world, and HIV-2, which occurs mainly in West Africa.
It is commonly assumed that replication of the virus takes place in several main steps:                1—Fixation or attachment to a target cell        2—Fusion, penetration and decapsidation        3—Reverse transcription        
This step is specific to retroviruses: in fact, as the latter have RNA and not DNA for their genome, an operation of transcription, “converting” viral RNA to viral DNA, which alone can be integrated in the genome of the target cell, is necessary. This transcription is performed by the enzyme reverse transcriptase (RT).                4—Integration        
The double-stranded DNA thus formed, closely associated with integrase and other viral and cellular protein components in a complex called preintegration complex, enters the cell nucleus. The DNA is then integrated randomly in the genome of the target cell, under the action of the enzyme integrase.                5—Formation of messenger RNA (mRNA)        6—Splicing of the mRNA thus obtained        7—Translation of the mRNA        8—Maturation        9—Assembly        
The structural proteins of the virus (matrix, capsid and nucleocapsid) are produced in the form of polyproteins. At the end of the maturation step, the various proteins are linked together and are transported to the membrane of the target cell, where they join the viral membrane glycoproteins. Viral RNAs join the viral proteins. The structural proteins assemble to form the capsid (protein envelope covering the DNA or RNA, the whole being denoted by nucleocapsid) and the matrix, which surrounds this assembly.                10—Budding        
The capsid emerges from the infected cell.                11—Maturation of the viruses        
A viral protease cleaves the bonds that join the various structural proteins (matrix, capsid and nucleocapsid). Following these cleavages, the virions (viral particles together with their outer protein envelope (capsid) and their RNA or DNA molecules inside) then become infectious and are ready to infect new cells.
Once seropositivity has been established, regular monitoring of the patient is put in place. Two main factors are usually monitored in order to track the development of the disease:
1—The level of CD4+ T lymphocytes
The level of CD4+ T lymphocytes has been used for monitoring the progression of infection towards immune deficiency caused by HIV. The CD4+ T lymphocyte count corresponds to the number of T4 cells present in the blood. A normal level in humans is between 500 and 1500 CD4+T/mm3 of blood. It had generally been assumed that:                up to 500 CD4+T/mm3 of blood, the patient can live normally without requiring treatment;        starting from 350 CD4+T/mm3 of blood, the offer of antiviral treatment is to be discussed, the expected result being control of the reproduction activity of the HIV, and, additionally, an at least partial rise in the CD4+T level;        below 200 CD4+T/mm3 of blood, the patient is regarded as immunodepressed, running the risk of contracting diseases defining full-blown AIDS. Antiviral treatment with or without antibiotic prophylaxis is the only treatment capable of avoiding these complications.        
From 2015 onwards, WHO and NIH-NAID headquarters recommend antiviral combinations therapy to be taken by all HIV carriers as soon as detected, whatever their blood CD4 levels with the purpose to reduce chances of AIDS and non-AIDS related diseases, and the intimate transmission of the virus. Indeed, based on updated knowledge, it is generally accepted that a patient whose plasma viral load is below 50 copies/ml can be considered by law as a “non-transmitter of infection” by the mucosal route.
2—Viral Load
The concentration of HIV viral particles in a volume of blood gives an objective estimate of the total number of virions freshly produced by the infected subject's body.
Measurement is made according to standardized methods that vary little from one laboratory to another if it uses these validated methods. The result is given in log 10 of the copy number/ml. The error in quantification (copy number of the virus) is such that a variation less than or equal to 0.5 is said to be not significant.
The difference between two measurements of viral load taken with a time interval allows the rate of reproduction of HIV to be evaluated and therefore the development of the infection. It is now generally understood that there is a loose link between the viral load and the level of immune deficiency, manifested by the disappearance of CD4+ T lymphocytes.
At the date of the present invention, the viral load is the best indicator of the development of the virus in the patient; based on current knowledge, it has generally been accepted that a patient whose plasma viral load is below 50 copies/ml can be considered as a “non-transmitter of infection” by the mucosal route.
At the date of the present invention, there is no pharmaceutical composition for definitively eradicating HIV in a person who has contracted the virus, but certain compositions are able to suppress the HIV replication, said control being demonstrated by maintenance of a viral load constantly below 50 copies/ml of plasma. This control is able to stop progression of the disease to AIDS, and gives a life expectancy for the HIV carrier, correctly treated, near or equal to that of persons of the same age and of the same sex.
Since the beginning of the 1980s, numerous studies have led to the identification of a large number of antiretrovirals whose function is to interfere and block the various mechanisms required for replication of the HIV virus, by targeting more particularly one or other enzyme of HIV required for its replication or by affecting the physicochemical mechanisms governing entry of the virus into the target cell.
At the date of the present invention, antiretrovirals constitute the only medicinal products usefully employed against HIV. The first and principal objective of this therapy, notably in a patient who is naive of any treatment, is to keep the viral load below the detection threshold of 50 copies/ml of plasma for as long as possible, otherwise the antiviral therapy risks losing its efficacy over time, owing to the emergence of viruses that are resistant to the antiviral drugs administered (Hammer S M, Saag M S, Schechter M, et al., Treatment for adult HIV infection: 2006 recommendations of the International AIDS Society-USA panel. Top HIV Med (2006) 14:827-43)
The anti-HIV drugs are classified in four main classes of antiretrovirals, differing in their mode of action on the HIV virus and against its reproduction and/or its propagation in the carrier's body:
First there are the inhibitors of reverse transcriptase, which inhibit the conversion of viral RNA to proviral DNA, the first step in replication of the virus from the viral RNA. In this class, a distinction is made between:                nucleoside or nucleotide inhibitors of reverse transcriptase (NRTI); and        non-nucleoside inhibitors (NNRTI)        
The NRTIs correspond to the first class of antiretrovirals that were marketed. As examples of NRTI compounds, we may mention zidovudine (AZT, Retrovir®) and stavudine (d4T, Zerit®) (two thymidine analogs), didanosine (ddI, Videx®), abacavir (ABC, Ziagen®) and tenofovir (TDF, Viread®) (three adenosine analogs), and lamivudine (3TC, Epivir®) and emtricitabine (FTC, Emtriva®) (two cytosine analogs).
The NNRTIs are powerful selective inhibitors of HIV reverse transcriptase. As examples of NNRTI compounds we may mention nevirapine (NVP, Viramune®), etravirine (ETV, Intelence®), and efavirenz (EFV, Sustiva®). They are only active against HIV-1.
Next there are the inhibitors of HIV protease (PI) which act by inhibiting the action of the enzyme that directs the exact cutting of the viral proteins that are precursors of structures required for formation of the infectious HIV material, and notably the HIV virions, which are able to propagate in the organism and infect new permissive cells. Under the action of the inhibitors of HIV protease, pseudovirions are obtained, which are unable to infect new cells. As examples of PI compounds, we may mention, in their historical order of marketing, saquinavir (SQV, Invirase®), ritonavir (RTV, Norvir®), indinavir (IDV, Crixivan®), amprenavir (APV, Agenerase®), nelfinavir (NFV, Viracept®), atazanavir (ATZ, Reyataz®), fosamprenavir (FPV, Telzir®), tipranavir (TPV, Aptivus®), and darunavir (DRV, Prezista®).
Each of these PIs has the pharmacokinetic property of being eliminated rapidly from the patient's body by the cytochrome P450 pathway; partial blocking of this route of elimination by a product such as ritonavir, a powerful inhibitor of the cytochrome P450 functions, greatly prolongs the pharmaceutical lifetime of the PI prescribed. Ritonavir given at low doses “boosts” the anti-HIV protease administered to the patient at the same time, by increasing the levels in the blood, and prolonging its useful half-life in the organism.
There are also integrase inhibitors, which block the action of an enzyme of HIV whose elective function is to trim the ends of the HIV proviral DNA so as to make this DNA suitable to serve as a template for the transcription of the proviral DNA to HIV RNA. The integrase inhibitors make this enzyme instantly incapable of its function of DNA trimming, thus preventing reproduction of the viral genome in its target cell. As examples of integrase inhibitor compounds, we may mention raltegravir and elvitegravir (GS 9137). The integrase inhibitors include two main groups: the Integrase Strand Transfer Inhibitors (INSTI) and the Integrase Binding Inhibitors (INBI).
Finally there are the fusion-lysis inhibitors, which are involved before the start of the biochemical cycle of HIV replication, by blocking the infectious progress of HIV at the level of certain proteins present on the surface of the virions, or by interfering with the binding capacities of these surface proteins with co-receptors that are present themselves on the surface of target cells of HIV. As examples of fusion-lysis inhibitor compounds, we may mention enfuvirtide (Fuzeon®) and maraviroc (Celsentri®).
Administered alone, most of the antiretrovirals have been shown to be only partially effective, and are generally incapable of sufficiently blocking the reproduction of HIV to obtain an optimum reduction in viral load or prevent it increasing again.
To overcome this deficiency, many combination therapies, and in particular triple therapies, have been developed over the years.
Triple therapy consists of the co-administration of three antiretrovirals, in the form of three different medicinal products administered separately, or in the form of a unit dosage form containing the three active principles.
Thanks to these combination therapies, and in particular the triple therapies used since 1996, mortality due to AIDS has been reduced significantly.
Based on their demonstrated efficacy, and their acceptability, the preferred antiretroviral combinations for starting anti-HIV therapy in patients without prior treatment have as their basis combinations of two NRTIs combined either with a PI boosted with ritonavir, or an NNRTI (Gazzard B. British HIV Association (BHIVA) guidelines for treatment of HIV-infected adults with antiretroviral therapy (2006). HIV Med (2006) 7:487-503).
Exceptionally, a third reverse transcriptase inhibitor is added to the combination consisting of a pair of nucleosides and an NNRTI to form a quadruple therapy, but the latter, as well as triple therapies combining three NRTIs, have not generally been validated.
Among the triple therapies available at the date of the present invention, there are triple therapies combining:                a pair of NRTIs selected from:                    lamivudine or emtricitabine, and zidovudine;            lamivudine or emtricitabine, and stavudine (however, these last two pairs of nucleoside analogs are generally ignored by prescribers because of their undesirable metabolic effects);            lamivudine or emtricitabine and abacavir;            lamivudine or emtricitabine and tenofovir; or            lamivudine or emtricitabine and didanosine;                        with the combination of ritonavir with a PI selected from lopinavir, fosamprenavir, atazanavir and darunavir; or with an NNIRT selected from nevirapine, efavirenz and etravirine.        
However, many triple therapies available at the date of the present invention are characterized by viral breakthroughs, i.e. a viral load in the patient above 100 copies/ml of plasma measured during two close consecutive dosages; the level of “viral breakthroughs” increasing with the years of uninterrupted administration. In these cases, the level of breakthroughs rises to 10% or more of patients treated after just 48 weeks of treatment, and can exceed 20% or even 30% after 3 or 4 years of uninterrupted treatments. These breakthroughs are a sign of suboptimal antiviral combinations, and put forward many situations in which there may be a selection of HIV viruses bearing mutations of at least partial resistance to the medicinal components of the combination (First-line antiretroviral therapy with efavirenz or lopinavir/ritonavir plus two nucleoside analogues: the SUSKA study, a non-randomized comparison from the VACH cohort, Pere Domingo et al., Journal of Antimicrobial Chemotherapy (2008) 61, 1348-1358). This is the case in particular with most triple therapies combining only three reverse transcriptase inhibitor components and triple therapies combining two reverse transcriptase inhibitor components with nevirapine. (Risk of Early Virological Failure of Once-Daily Tenofovir-Emtricitabine plus Twice-Daily Nevirapine in Antiretroviral Therapy-Naive HIV-Infected Patients, Giuseppe Lapadula, Silvia Costarelli, Eugenia Quiros-Roldan, et al., Clinical Infectious Diseases 2008, 46:1127-1129; and High rate of early virological failure with the once-daily tenofovir/lamivudine/nevirapine combination in naive HIV-1-infected patients-authors' response, D. Rey, B. Hoen, P. Chavanet, et al., J. Antimicrob. Chemother 2009; 63: 1080-1081).
Furthermore, many undesirable side effects are associated with the use of these drugs, including lactic acidosis, characterized by deep, rapid breathing, somnolence, nausea, vomiting and/or stomach pains; sensations of vertigo; sleep disorders; difficulty concentrating; abnormal dreams; skin rashes; various inflammations or infections; and/or bone disorders, etc.
The number of triple therapies available at the date of the present invention means that each HIV patient can be administered different compositions during the treatment so that said treatment can be best adapted to the development of the infection and to the patient's tolerance. However, the need for daily administration seven days a week makes these therapies onerous and restricting for the patients, and tends to increase the intensity of the side effects that they experience.
At the date of the present invention two triple therapies (Trizivir®, a medicinal product marketed by the GlaxoSmithKline pharmaceutical laboratory and Atripla®, a medicinal product marketed by the Gilead pharmaceutical laboratory) allow daily administration of the treatment seven days a week as a unit dosage form.
Trizivir® is in the form of a single film-coated tablet comprising:                150 mg of lamivudine;        300 mg of zidovudine; and        300 mg of abacavir base (351 mg of abacavir sulfate).        
Atripla® is in the form of a single film-coated tablet comprising:                600 mg of efavirenz;        200 mg of emtricitabine; and        245 mg of tenofovir disoproxil fumarate (expressed as tenofovir disoproxil).        
This second pharmaceutical composition, which is among the most effective triple therapies currently marketed, nevertheless requires daily administration seven days a week, which certainly does not promote best patient compliance with the treatment.
Moreover, neither Atripla®, nor Trizivir® has been able to reduce the undesirable effects mentioned above.
Since 2009, a number of all-in-one antiviral combo pills have come to the market: 1) EVIPLERA (Gilead Science) combines rilpivirine (NNRTI), tenofovir (NRTI) and emtricitabine (NRTI); 2) TRIUMEQ (ViiV) combines dolutegravir (INSTI), abacavir (NRTI) and lamivudine (NRTI); 3) STRIBILD (Gilead Science) combines elvitegravir (INSTI), cobicistat (Booster), tenofovir (NRTI) and emtricitabine (NRTI).
However, these new products require a daily administration seven days a week and have not been able to reduce the undesirable effects mentioned above.
Finally, the cost per patient and per year of the combination therapies available at the date of the present invention is still excessively high. For example, Atripla® is sold in France in the form of a bottle containing 30 tablets (i.e. a month of treatment) at the price of 834.30 , or an annual cost per patient of about 10,000 . Now, although the current treatments can greatly limit the development of the HIV virus in patients, in no case are they able to eradicate it. The cost of treating persons with HIV can therefore reach very substantial sums, which are likely to increase considerably in future.
In 2007, an isolated study attempted to demonstrate that it was possible to reduce the weekly administration of various existing triple therapies to five days (Pilot Study of a Novel Short-Cycle Antiretroviral Treatment Interruption Strategy: 48-Week Results of the Five-Days-On, Two-Days-Off (FOTO) Study, Calvin J. Cohen, M D, Amy E. Colson, Alexander G. Sheble-Hall, et al., HIV Clin Trials 2007; 8(1):19-23). In this study, conducted on thirty patients whose HIV virus is controlled durably by various uninterrupted triple therapies, the weekly treatment regimen was reduced to five days per week (with two days off). At the 24th and 48th week of this treatment, the virus was still under control in 26 out of 29 patients (89.6%). However, even the authors admit that the benefits seen in the “FOTO” study are still very uncertain and these dosage regimens should not be used before these results are confirmed in a larger study. Moreover, this document gives no indication regarding the possibility of a possible further reduction in the number of weekly administrations of the existing triple therapies. In particular, it emphasizes that intermittent treatments should be reserved for triple therapies with a non-nucleoside antiretroviral agent, such as efavirenz or nevirapine, with a long natural life-time in the body, thus ruling out combinations comprising agents having a short plasma half-life, such as the antiproteases (PI).
However, these studies have remained isolated and, at the date of the present invention, most specialists agree in considering that a decrease in the number of weekly administrations of existing triple therapies would increase the number of viral breakthroughs in the patients treated. Thus, a decrease in the number of weekly administrations of existing triple therapies is generally associated with certain therapeutic failure. As an example, Professor Delfraissy regards noncompliance with the treatment as the main cause of therapeutic failure (“Therapeutic management of persons infected with HIV-Report 2004-Under the supervision of Professor Jean-François Delfraissy, 2004, Éditions Flammarion, p. 48-49).
Moreover, a study published after the “FOTO” study (Relationship between Adherence Level, Type of the Antiretroviral Regimen, and Plasma HIV Type 1 RNA Viral Load: A Prospective Cohort Study, M. Martin, E. Del Cacho, C. Codina, et al., AIDS Research and Human Retroviruses, October 2008, 24(10): 1263-1268. doi:10.1089/aid.2008.0141) well summarizes the predominant prejudice according to which reducing the amount of antivirals in a patient must lead to a resumption of HIV replication, in inverse proportion to the pressure exerted daily by the triple therapy in question. Thus, compared with patients observing the prescribed treatment at more than 90%, this study notes a risk of viral breakthrough:                9 times greater in patients only complying with the treatment at 80 to 89.9%, or, for triple therapy assuming daily administration seven days a week, for patients taking their treatment about six days out of seven;        45.6 times greater in patients only complying with the treatment at 70 to 79.9%, or, for triple therapy assuming daily administration seven days a week, for patients taking their treatment about five to six days out of seven; and        77.3 times greater in patients only complying with the treatment at less than 70%, or, for triple therapy assuming daily administration seven days a week, for patients taking their treatment less than five days out of seven.        
Moreover, another study also published after the “FOTO” study (Not all missed doses are the same: sustained NNRTI treatment interruptions predict HIV rebound at low-to-moderate adherence levels, Parienti J J, Das-Douglas M, Massari V, Guzman D, Deeks S G, Verdon R, Bangsberg D. R., PLoS One, Jul. 30, 2008; 3(7):e2783) teaches that any interruption of treatment of more than 2 days increases the risks of virological “rebound”, i.e. the risks of a resumption of HIV replication.
However, it was discovered completely unexpectedly that certain combination therapies could be administered to the patient according to an administration regimen different from that recommended and used in the context of HIV treatment at the date of the present invention, permitting a marked decrease in the number of weekly administrations of the treatment, but without affecting or lowering the efficacy of the latter.